1. Technical Field
The present invention relates to a sheet manufacturing apparatus and a sheet manufacturing method.
2. Related Art
Depositing a fiber-like material and causing a bonding force between the deposited fibers to obtain a sheet-like or film-like formed body has been performed for a long time. Typical examples thereof include manufacturing paper by pulp molding (paper-forming) using water. Even in present times, pulp molding is widely used as an example of a method of manufacturing paper. The paper manufactured by pulp molding generally includes a structure by cellulose fibers derived from wood or the like being entangled with one another, and being partially bonded to one another by a binder (paper strengthening agent (such as a starch paste and a water-soluble resin)).
According to the pulp molding, it is possible for the fibers to be deposited in a state where uniformity is favorable, and, in a case where a paper strengthening agent is used in the bonding between fibers, it is possible for the paper strengthening agent to be dispersed (distributed) in a state where the uniformity in the paper surface is good. However, because the pulp molding is a wet method, it is necessary to use large volumes of water, and the necessity of dewatering and drying, or the like, arises after forming the paper, and therefore the energy or time consumed is extremely large. It is necessary to suitably process the water used as waste water. Accordingly, it is difficult to respond to modern demands for energy savings, environmental protection, and the like. The apparatuses used in pulp molding frequently need large scale utilities such as water, power, and drainage facilities, and size reductions are difficult. From this viewpoint, there is an expectation of methods, referred to as dry methods that use no or almost no water as paper manufacturing methods in place of pulp molding.
For example, in the technology disclosed in JP-A-2011-099172, an attempt at bonding fibers to one another with a thermal fusion-bondable resin in air-laid non-woven fabric that includes a highly water absorbent resin is disclosed.
However, in the technology disclosed in JP-A-2011-099172, the thermal fusion-bondable resin has the properties of a powder, and there is a danger of detachment from between the fibers when air-laid. Paragraph [0013] in JP-A-2011-099172 discloses that when thermal fusion-bondable powder is too small, the powder passes through the mesh conveyor (mesh belt) and it is difficult for the fibers to be bonded to one another. Accordingly, JP-A-2011-099172 describes that it is favorable to use a thermal fusion bondable resin powder of the comparatively large particle diameter (20 mesh pass to 300 mesh on).
However, when the particle diameter of the resin is large, the uniformity of the distribution of the resin in the manufactured sheet may be impaired. Accordingly, it is desirable that the particle diameter of the resin is smaller in order for the resin to be uniformly dispersed between the fibers.
In a case of forming a web by air-laying, suctioning is ordinarily performed from below the mesh belt. Thus, when the particle diameter of the resin is smaller than the size of the openings in the mesh belt, it is thought that the resin easily detaches from between the fibers during web formation. Therefore, even if the particle diameter of the resin is reduced, work is necessary to make the resin difficult to detach from between the fibers.